Electroplated copper interconnection structure, process for making and electroplating bath

ABSTRACT

Interconnect structures with copper conductors being at least substantially free of internal seams or voids are obtained employing an electroplating copper bath containing dissolved cupric salt wherein the concentration of the salt is at least about 0.4 molar and up to about 0.5 molar concentration of an acid. Also provided are copper damascene structures having an aspect ratio of greater than about 3 and a width of less than about 0.275 μm and via openings filled with electroplated copper than is substantially free of internal seams or voids.

TECHNICAL FIELD

[0001] The present invention relates to interconnection wiring onelectronic devices such as on integrated circuit (IC) chips and moreparticularly to substantially void-free and seamless submicronstructures fabricated by copper electroplating from novel plating baths.

BACKGROUND OF INVENTION

[0002] AlCu and its related alloys are preferred alloys for forminginterconnections on electronic devices such as integrated circuit chips.The amount of Cu in AlCu is typically in the range from 0.3 to 4percent.

[0003] Replacement of AlCu by Cu and Cu alloys as chip interconnectionmaterial results in advantages of performance. Performance is improvedbecause the resistivity of Cu and certain copper alloys is less than theresistivity of AlCu; thus narrower lines can be used and higher wiringdensities will be realized.

[0004] The advantages of Cu metallization have been recognized by thesemiconductor industry. In fact, the semiconductor industry is rapidlymoving away from aluminum and is adopting copper as the material ofchoice for chip interconnects because of its high conductivity andimproved reliability.

[0005] MAnufacturing of chip interconnects involves many process stepsthat are interrelated. In particular, copper interconnects aremanufactured using electroplating in a process called “Dual Damascene”in which a via and a line are fabricated together in a single step. Theelectroplating process, typically, employs a plating solution composedof cupric sulfate salt, sulfuric acid, inorganic and organic additivesthat control the process such that the rate of copper electrodepositionis differentially inhibited along the sidewall of a small feature,resulting in preferential deposition at the bottom wall of the feature.This phenomenon is called superfilling.

[0006] A few of the important integration challenges that need to beovercome to successfully fabricate Dual Damascene copper interconnectsare assuring the continuity of the barrier and seed layer films andproviding a copper electroplating process capable of producing seamlessand void-free deposits at the feature sidewalls and bottom wall of thefeature and along the center of the wiring. Furthermore, theInternational Technology Roadmap for Semiconductors, 1999 Edition, callsfor smaller via diameters and higher aspect ratios in futureinterconnect metallizations.

[0007] With the shrinking dimensions there is a continuing challenge tofill these features with copper without a seam or void. In DualDamascene fabrication of features with linewidths of 0.25 μm or smaller,typically a via and a line have to be filled in one process stepemploying copper electroplating. The applied current is carried througha thin seed copper layer. Often, the seed layer is extremely thin,possibly discontinuous and oxidized and thus it is not capable ofcarrying the electroplating current reliably within small features ofhigh aspect ratios. In sub-micron vias, which are typically moredifficult to fill than lines, the rate of diffusion of the cupric ionsdissolved in the plating solution is too low to keep up with the rate ofreduction of cupric ions at the metal surface. As a result, the cupricion concentration within a via becomes much lower than the cupric ionbulk concentration and the concentration overpotential becomes large.The superfilling capability of the plating solution provided by theorganic additives cannot overcome the large concentration overpotentialcaused by the depletion of the cupric ion. These phenomena manifestthemselves as voids along the sidewall of the features, two types ofdefects, caused by missing copper seed layer, and voids or seams alongthe feature centerline, caused by the depletion of the cupric ion withinthe via.

[0008] Accordingly, there exists a need to provide a copperelectroplating process that can accomplish Dual Damascene plating atsmall features without internal seams or voids.

SUMMARY OF INVENTION

[0009] The present invention relates to providing a highly reliablecopper interconnect structure suitable for wiring in integrated circuitchips with at least substantially, if not entirely, void-free seamlessconductors.

[0010] In particular, an aspect of the present invention relates to aprocess for fabricating an interconnect structure on an electronicdevice with copper conductor substantially free of internal seams orvoids.

[0011] The process of the present invention comprises:

[0012] forming an insulating material on a substrate,

[0013] lithographically defining and etching recesses for lines and/orvias in the insulating material in which interconnection conductormaterial will be deposited,

[0014] depositing a barrier layer against copper diffusion onto theinsulating materials, and into the etched recesses, depositing a copperseed layer for conducting electrical current during electroplating, and

[0015] depositing the copper conductor by electroplating from anelectroplating bath.

[0016] The electroplating bath comprises a high copper concentrationwherein the concentration of the cupric salt is at least about 0.4 molarand up to the saturation concentration of the cupric salt in solution.In addition, the bath contains an acid and can contain other commoncomponents of acid copper plating baths, such as inorganic and organicaddition agents.

[0017] The copper conductor is deposited by electroplating using anelectroplating process in the above electroplating bath wherein thesubstrate to be plated is introduced into the plating bath with thepower supply enabled such that a plating current is imposed at theinstant of contact of the substrate with the plating bath. The initiallyimposed plating current with the power supply engaged is from 1 to 20mA/cm² and the time at this lower current density is from 0 to 40seconds, subsequently the power supply is switched to a higher currentdensity of 10 to about 50 mA/cm². The initial and final currentdensities may also be the same so that the substrate is introduced intothe plating bath with the same imposed current as the copper platingcurrent.

[0018] The present invention also relates to interconnect structuresobtained by the above disclosed process.

[0019] Another aspect of the present invention relates to a copperelectroplating bath that comprises a high concentration of a dissolvedcupric salt of at least about 0.4 molar and a low sulfuric acidconcentration of at most 0.5 molar and as low as 0.01 molar. Inaddition, the bath can contain other common components of acid copperplating baths such as inorganic and organic addition agents.

[0020] The present invention further relates to a copper damascenestructure having an aspect ratio of greater than 3 and a width ordiameter of less than 0.275 μm which comprises:

[0021] a substrate having a dielectric layer having a via and lineopening therein;

[0022] the via and/or line opening having a barrier layer on sidewallsand bottom surfaces of the via and/or line opening;

[0023] a metal seed layer on the barrier layer; and

[0024] wherein the via and/or line opening are filled with electroplatedcopper forming a continuous interface with the liner or barrier layerand being substantially free of internal seams or voids.

[0025] Still other objects and advantages of the present invention willbecome readily apparent by those skilled in the art from the followingdetailed description, wherein are shown and described preferredembodiments of the invention, simply by way of illustration of the bestmode contemplated of carrying out the invention. As will be realized theinvention is capable of other and different embodiments, and its severaldetails are capable of modifications in various obvious respects,without departing from the invention. Accordingly, the description is tobe regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF FIGURES

[0026]FIG. 1 is a SEM cross section of vias filled with electroplatedcopper according to prior art method.

[0027]FIG. 2 is a SEM cross section of vias filled with electroplatedcopper according to prior art method.

[0028]FIG. 3 is a SEM cross section of vias filled with electroplatedcopper according to prior art.

[0029]FIGS. 4A and 4B are SEM cross sections of vias filled withelectroplated copper according to the present invention.

[0030]FIGS. 5A and 5B are SEM cross sections of vias filled withelectroplated copper according to the present invention.

[0031]FIG. 6 is a SEM cross section of vias filled with electroplatedcopper according to the present invention.

BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION

[0032] The present invention relates to a process for fabricating aninterconnect structure on an electronic device with copper conductorsthat are substantially, if not entirely, free of internal seams orvoids. The fabrication process comprises forming an insulating materialsuch as silicon dioxide on a substrate (e.g. a semiconductor wafersubstrate).

[0033] Lines and/or vias openings are lithographically defined andformed in the insulating material by well known techniques. According topreferred aspects of the present invention, the lines and/or vias have awidth of less than about 0.275 μm, and more preferably about 0.2 μm orless, including widths of about 0.1 μm.

[0034] In addition, according to the present invention the lines and/orvias have aspect ratios of greater than about 3.

[0035] According to the present invention, copper is deposited in thelines and/or vias by electroplating from a bath containing a dissolvedcupric salt wherein the concentration of the cupric salt is at leastabout 0.4 molar and preferably at least about 0.8 molar. The maximumamount is up to the solubility limit of the salt. The preferred salt isCuSO₄. The cupric ion may also be added as sulfamate, hydroxide,carbonate, or other salt that is compatible with the plating bathchemistry and the addition agents. The concentration of the cupric saltis typically about two to four times higher than the concentrationsnormally used in prior art baths.

[0036] The electroplating bath of the present invention can include upto about 0.5 molar of an inorganic acid. The electroplating bath moretypically contains an amount up to about 0.5 molar, and preferably about0.1 to about 0.25 molar concentration of an inorganic acid. Thepreferred acid is H₂SO₄. Alternatively sulfonic acid, methane sulfonicacid, hydrochloric acid or other acids with comparable bath function canbe added. The concentration of the acid is typically at least aboutthree to four times lower than the concentration normally used in priorart electroplating baths.

[0037] The electroplating bath typically has an acidic pH up to about 5and preferably about 0.6.

[0038] Employing electroplating baths according to the present inventionmakes possible seamless void-free Dual Damascene copper electrofill thatis extendible to 0.10 micron dimensions. Also, such baths provide a wideand robust process window.

[0039] The electroplating baths employed according to the presentinvention preferably are free of complexing agents that are often usedin electroplating baths with low acid concentrations.

[0040] In addition, the plating baths of the present invention canoptionally contain auxiliary additives for achieving superfilling andcontrolling such properties of the electroplated copper as grainstructure, ductility and internal stress. Typical additives and theirrelative amounts are disclosed in PCT/US96/19592, disclosure of which isincorporated herein by reference.

[0041] One suitable system of additives is marketed by Enthone-OMI, Inc.and is known as the Sabre Copper MAke-up. The composition includes twoadditives one referred to as Sabre B and the other Sabre-L. Two othersuitable systems of additives are marketed by ShipleyRonal, Inc. One ofthem is known as the Copper Gleam 2001 system. The additives arereferred to by the manufacturer as Copper Gleam 2001 Leveller and CopperGleam 2001 Carrier. The other system of additives also marketed byShipleyRonal Inc. is known as Nanoplate 2001 system, which is atwo-additive configuration. One of the additives is referred to asC-2001 Suppressor Solution and the other is referred to as B-2001Additive Solution. Another suitable system of additives is marketed byAtotech USA, Inc. and is known as the Cupracid HS system. The additivesin this system are referred to by the manufacturer as CupracidBrightener and Cupracid HS Basic Leveller.

[0042] Examples of specific additives which may be added to a bath inthe instant invention are described in several patents. U.S. Pat. No.4,110,176 issued Aug. 29, 1978 to H-G Creutz, deceased, et al., entitled“Electrodeposition of Copper” describes the use of additives in aplating bath such as poly alkanol quaternary-ammonium salt to givebright, highly ductile, low stress and good leveling copper depositsfrom an aqueous acidic copper plating bath, which patent is incorporatedherein by reference.

[0043] U.S. Pat. No. 4,376,685 issued MArch 15, 1983 to A. Watson,entitled “Acid Copper Electroplating Baths Containing Brightening andLeveling Additives”, describes additives to a plating bath such asalkylated polyalkyleneimine to provide bright and leveled copperelectrodeposits from an aqueous acidic bath, which patent isincorporated herein by reference.

[0044] U.S. Pat. No. 4,975,159 issued Dec. 4, 1990 to W. Dahms, entitled“Aqueous Acidic Bath for Electrochemical Deposition of a Shiny andTear-Free Copper Coating and Method of Using Same”, describes adding toan aqueous acidic bath combinations of organic additives including atleast one substituted alkoxylated lactam as an amide-group-containingcompound in an amount to optimize the brightness and ductility of thedeposited copper, which patent is incorporated herein by reference. InU.S. Pat. No. 4,975,159, Table I lists a number of alkoxylated lactamswhich may be added to a bath in the instant invention. Table II lists anumber of sulfur-containing compounds with water-solubilizing groupssuch as 3-mercaptopropane-1-sulfonic acid, which may be added to a bathin the instant invention. Table II lists organic compounds such aspolyethylene glycol which may be added to a bath as surfactants in theinstant invention.

[0045] U.S. Pat. No. 3,770,598 issued Nov. 6, 1973 to H-G Creutz,entitled “Electrodeposition of Copper from Acid Baths”, describes bathsfor obtaining ductile, lustrous copper containing therein dissolved abrightening amount of the reaction product of polyethylene imine and analkylating agent to produce a quaternary nitrogen, organic sulfidescarrying at least one sulfonic group, and a polyether compound such aspolypropylene glycol, which patent is incorporated herein by reference.

[0046] U.S. Pat. No. 3,328,273 issued Jun. 27, 1967 to H-G Creutz etal., entitled “Electrodeposition of Copper from Acidic Baths”, describescopper sulfate and fluoborate baths for obtaining bright, low-stressdeposits with good leveling properties that contain organic sulfidecompounds of the formula XR1-(Sn)-R₂—SO₃H, where R₁ and R₂ are the sameor different and are polymethylene groups or alkyne groups containing1-6 carbon atoms, X is hydrogen or a sulfonic group, and n is an integerof 2-5 inclusive, which patent is incorporated herein by reference.Additionally, these baths may contain polyether compounds, organicsulfides with vicinal sulphur atoms, and phenazine dyes. In U.S. Pat.No. 3,328,273, Table I lists a number of polysulfide compounds which maybe added to a bath in the instant invention. Table II lists a number ofpolyethers which may be added to a bath in the instant invention.

[0047] Additives may be added to the bath for accomplishing variousobjectives. Additives may be included for inducing in the conductorspecific film microstructures including large grain size relative tofilm thickness or randomly oriented grains.

[0048] In addition, prior to the electroplating, a liner or barrierlayer is provided on the sidewalls and bottom surfaces of the linesand/or vias. Typical liner or barrier layers include Ti, Ta, W andnitrides thereof. The total thickness of the liner or barrier layer(s)is typically about 0.025 μm to about 0.1 μm.

[0049] Located on the surfaces of the liner or barrier layer istypically a metal seed layer such as copper. The seed layer is typicallyabout 0.01 μm to about 0.25 μm thick.

[0050] The plating process is preferably carried out by introducing thesubstrate (e.g. the wafer) into the plating bath with the current on sothat the thin and possibly oxidized seed layer is cathodicallyprotected. If the seed layer is oxidized it can be reduced back tocopper and repair itself during the hot immersion process.

[0051] According to preferred processing of the present invention, thecurrent upon initial immersion of the wafer is lower than that employedin the electroplating such as about 1-5 mA/cm². The initial current istypically maintained for up to about 40 seconds. If the initial currentdensity employed is lower than the desired electroplating currentdensity, the current density can be increased at this time (after theinitial period) to a current density typical of the prior art processessuch as between 10 mA/cm² and 50 mA/cm². The current can be maintainedat the electroplating current density until the desired thickness isachieved.

[0052] The lower acid concentration in the bath tends to provide forimproved seed layer integrity because the lower acid strength does nothave as high tendency to attack or dissolve the copper or oxidizedcopper seed layer. In addition, the lower acid concentration makes itpossible to dissolve the necessary increased concentration of cupricsalt in the bath.

[0053] The increased cupric ion concentration makes it possible to avoida large concentration overpotential in high aspect ratio features. Inthe absence of a large concentration overpotential, the additives canproduce superfilling at the center-line of the features and voids willnot occur. The high cupric ion concentration in the plating bath alsoexpands the process window of copper electrofill down to 0.1 microndimensions because it minimizes depletion of the cupric ion within thevias. In essence, a high copper-low acid bath can fill very small widthor diameter and high aspect ratio Dual Damascene structures.

[0054] The plating is usually carried out at about normal roomtemperature.

[0055] In a typical process, after the electroplating planarizing orchemical-mechanical polishing of the resulting structure is carried outto accomplish electrical isolation of individual lines and/or vias.

[0056] The following non-limiting examples are presented to furtherillustrate the present invention.

EXAMPLE 1

[0057] A wafer having 0.25 μm vias with an aspect ratio of about 7 in asilicon dioxide insulating layer having a barrier layer about 0.05 μmthick and a copper seed layer about 0.15 μm thick is immersed in aplating bath containing 124 g/l CuSO_(4.5)H₂O, 49 g/l H₂SO₄, about 2 mMHCl, and about 10 ml/l of Sabre-B and about 1.8 ml/l of Sabre-L,commercially available additives from Enthone OMI. A current density ofabout 3.5 mA/cm² is applied and the wafer is immersed into the platingbath for about 10 seconds, after which the current is switched to 15mA/cm² and the plating continues for about 180 seconds. The wafer isrotated at about 120 rpm.

[0058]FIGS. 4A and 4B show SEM cross sections achieved by this example.As shown therein, filling of vias was excellent except for one via wherea void in the center of the via appeared.

EXAMPLE 2

[0059] A wafer having 0.25 μm vias with an aspect ratio of about 7 in asilicon dioxide insulating layer having a barrier layer about 0.05 μmthick and a copper seed layer about 0.15 μm thick is immersed in aplating bath containing about 248 g/l CuSO_(4.5)H₂O, about 24 g/l H₂SO₄,about 2 mM HCl, and about 10 ml/l of Sabre-B and about 1.8 ml/l ofSabre-30 L, commercially available additives from Enthone OMI. Uponimmersing the wafer into the bath, the current is switched on to 15mA/cm² and plating continues for about 180 seconds. The wafer is rotatedat about 120 rpm.

[0060]FIGS. 5A and 5B show SEM cross sections achieved by this example.As shown therein, filling of vias was excellent.

EXAMPLE 3

[0061] A wafer having 0.25 μm vias with an aspect ratio of about 7 in asilicon dioxide insulating layer having a barrier layer about 0.05 μmthick and a copper seed layer about 0.15 μm thick is immersed in aplating bath containing about 248 g/l CuSO_(4.5)H₂O, about 24 g/l H₂SO₄,about 2 mM HCl, and about 10 ml/l of Sabre-B and about 1.8 ml/l ofSabre-L, commercially available additives from Enthone OMI. A currentdensity of about 3.5 mA/cm² is applied and the wafer is immersed intothe plating for about 10 seconds, after which the current is switched to15 mA/cm² and the plating continues for about 180 seconds. The wafer isrotated at about 120 rpm.

[0062]FIG. 6 shows a SEM cross section achieved by this example. Asshown therein, filling of vias was excellent.

[0063] The process of turning the current on before closing theelectrical circuit between cathode and anode, prevents the seed layerfrom dissolving in the acidic plating bath and reduces any oxidizedcopper formed back to elemental copper. The current density applied canbe either the same as the electroplating current density or lower by asmuch as 15 times. A lower current density than the electroplatingcurrent density can be used for cathodic protection of the seed layerand to repair an oxidized seed layer.

[0064] The initial current is typically up to about 40 seconds employinga current density of about 1 to about 5 mA/cm².

COMPARISON EXAMPLE A

[0065] A wafer having 0.25 μm diameter vias with an aspect ratio of 4.8is immersed in a plating bath containing 159 g/l sulfuric acid and 60g/l copper sulfate pentahydrate and the same commercially availableadditives used in Example 3. The wafer is rotated at 60 rpm and thecurrent is off for 3 seconds while the wafer is in contact with theelectroplating solution. A current density of 15 mA/cm² is applied for180 seconds to electroplate copper.

[0066]FIG. 1 shows SEM cross section of vias filled according to thisexample. There are two kinds of voids observed: voids along the viasidewall and voids along the via centerline. The sidewall voids occurbecause the copper seed layer at this point on the sidewall wasinitially thin and was oxidized, the oxide layer then dissolving in theelectroplating solution during the 3 second-dwell time. Oxidation of thecopper seed layer can occur upon exposure to atmospheric oxygen ormoisture.

[0067] The other kind of void observed in FIG. 1 is a void along thecenterline of the copper deposit. Such voids are attributed to masstransport limitations of the cupric ion within the via and to theresulting large concentration overpotential. Typically additives in theplating solution yield a surface overpotential higher than the cupricion concentration overpotential, but in high aspect ratio vias or highaspect ratio Dual Damascene structures the cupric ion may be depletedfrom its bulk value by as much as 85% and the concentrationoverpotential may become higher than the surface overpotential thatproduces superfilling.

COMPARISON EXAMPLE B

[0068] A wafer having 0.25 μm diameter vias with an aspect ratio of 7 isimmersed in a plating bath containing 159 g/l sulfuric acid and 60 g/lcopper sulfate pentahydrate and the same commercially availableadditives used in Example 3. The wafer is rotated at 120 rpm and thecurrent is off for 3 seconds while the wafer is in contact with theelectroplating solution. A current density of 15 mA/cm² is applied for180 seconds to electroplate copper.

[0069]FIG. 2 shows SEM cross sections of vias filled according to thisexample. The same kinds of voids as present in Comparison Example A areevident in FIG. 2 as well.

COMPARISON EXAMPLE C

[0070] A wafer having 0.25 μm vias with an aspect ratio of about 7 in asilicon dioxide insulating layer having a barrier layer of about 0.05 μmthick and a copper seed layer about 0.15 μm thick is immersed in aplating bath containing about 60 μl CuSO_(4.5)H₂O, about 160 g/l H₂SO₄and the same commercially available additives and amounts used inexamples 3-5. A current density of about 3.5 mA/cm² is applied and thewafer is immersed into the plating bath for about 10 seconds, afterwhich the current is switched to 15 mA/cm² and the plating continues forabout 180 seconds. The wafer is rotated at about 120 rpm.

[0071]FIGS. 3A and 3B show SEM cross sections achieved by this example.As shown therein, large voids occurred in at least one via and smallervoids in other vias.

[0072] Furthermore, the copper deposited in the present invention hasproperties equivalent to copper deposited from prior art baths. The datain Table 1 below confirm that the resistivity of the copper metaldeposited from baths with high cupric sulfate concentration and lowsulfuric acid concentration is equivalent to the resistivity of copperdeposited from prior art baths. TABLE 1 Final Resistivity of PlatedFilms 60/160 126/47.6 223/46 223/26.6 (μΩ · CuSO₄.5H₂O/ CuSO₄.5H₂O/CuSO₄.5H₂O/ CuSO₄.5H₂O/ cm) H₂SO₄ (g/l) H₂SO₄ (g/l) H₂SO₄ (g/l) H₂SO₄(g/l) ρ 1.79 1.82 1.81 1.88

[0073] Additionally, there is no dependence of plating efficiency oncupric ion and acid concentrations.

[0074] The foregoing description of the invention illustrates anddescribes the present invention. Additionally, the disclosure shows anddescribes only the preferred embodiments of the invention but, asmentioned above, it is to be understood that the invention is capable ofuse in various other combinations, modifications, and environments andis capable of changes or modifications within the scope of the inventiveconcept as expressed herein, commensurate with the above teachingsand/or the skill or knowledge of the relevant art. The embodimentsdescribed hereinabove are further intended to explain best modes knownof practicing the invention and to enable others skilled in the art toutilize the invention in such, or other, embodiments and with thevarious modifications required by the particular applications or uses ofthe invention. Accordingly, the description is not intended to limit theinvention to the form disclosed herein. Also, it is intended that theappended claims be construed to include alternative embodiments.

What is claimed is:
 1. A process for fabricating an interconnectstructure on an electronic device with copper conductor substantiallyfree of internal seams or voids which comprises: forming an insulatingmaterial on a substrate; lithographically defining and forming recessesfor lines and/or vias in the insulating material in whichinterconnection conductor material will be deposited; depositing abarrier layer against copper diffusion; depositing a current carryingcopper seed layer; depositing the copper conductor by electroplatingfrom a bath containing a dissolved cupric salt wherein the concentrationof the cupric salt is at least about 0.4 molar and an acid and whereinthe bath has an acidic pH.
 2. The process of claim 1 wherein theconcentration of the cupric salt is at least about 0.8 molar.
 3. Theprocess of claim 1 wherein the cupric salt comprises CuSO₄.
 4. Theprocess of claim 1 wherein the concentration of the acid is an amount upto about 0.5 molar.
 5. The process of claim 1 wherein the concentrationof the acid is about 0.1 to about 0.25 molar.
 6. The process of claim 4wherein the acid is sulfuric acid.
 7. The process of claim 1 wherein theelectroplating bath has a pH of up to about
 5. 8. The process of claim 1wherein the electroplating bath has a pH of about 0.6.
 9. The process ofclaim 1 wherein the electroplating bath contains at least one auxiliaryadditive selected from the group consisting of brightener, levelingagent, ductility enhancer and stress reducer.
 10. The process of claim 1wherein the electroplating bath is free of complexing agents.
 11. Theprocess of claim 1 wherein the substrate is coupled to a plating powersupply with the current enabled before introducing the substrate intothe bath.
 12. The process of claim 11 wherein the initial current of thepower supply is lower than the current of the electroplating of copperfrom the bath onto the substrate.
 13. The process of claim 12 whereinthe initial current is maintained for up to about 40 seconds.
 14. Theprocess of claim 1 wherein the electroplating is carried out at acurrent density of about 10 to about 50 mA/cm².
 15. The process of claim13 wherein the initial current is about 1-5 mA/Cm².
 16. The process ofclaim 1 which further comprises depositing a barrier layer on sidewallsand bottom surfaces of the lines or vias, and depositing a metal seedlayer prior to electroplating the copper.
 17. The process of claim 16wherein the metal seed layer is copper.
 18. The method of claim 1wherein the vias or lines have dimensions of about 0.275 μm or less andaspect ratios of at least about
 3. 19. The method of claim 1 whichfurther comprises planarizing or chemical-mechanical polishing after theelectroplating.
 20. A copper damascene structure having an aspect ratioof greater than about 3 and a width of less than about 0.275 μm whichcomprises: a substrate having a dielectric layer having a via and/orline opening therein; the via and/or line opening having a liner orbarrier layer on sidewalls and bottom surfaces of the via opening; ametal seed layer on the liner or barrier layer; and wherein the viaand/or line opening is filled with electroplated copper that forms acontinuous interface with the liner or barrier layer and beingsubstantially free of internal seams or voids.
 21. An interconnectstructure obtained by the process of claim
 1. 22. An electroplatingcopper bath comprising dissolved cupric salt at a concentration of atleast about 0.4 molar, up to about 0.5 molar concentration of an acidand having an acidic pH.
 23. The bath of claim 22 being free ofcomplexing agent.
 24. The bath of claim 23 wherein the cupric saltconcentration is at least about 0.8 molar.